1. FIELD OF THE INVENTION:
The invention relates to an improved ball valve assembly for subterranean wells of the type wherein a spherical ball, having a cylindrical fluid passage therethrough, is rotated relative to an annular valve seat through an angle of 90.degree. to effect the shifting of the fluid passage from a position transverse to the bore of an annular valve seat to a position aligned with the bore of the annular valve seat.
2. DESCRIPTION OF THE PRIOR ART:
A ball valve is one of the most popular types of valves employed in subterranean wells for the control of fluid passing through a conduit. Ball valves are commonly found in safety valves and test trees. For example, a pair of typical ball valves for a test tree are described and illustrated in my co-pending application, Ser. No. 064,455, filed Aug. 6, 1979, now U.S. Pat. No. 4,306,623, entitled "Valve Assembly For A Subterranean Well Conduit", and assigned to the Assignee of this application.
A typical ball valve embodies a spherically shaped element having a fluid passage through its center. An annular seal cooperates with a spherical segment portion of the surface of the ball valve and maintains sealing relationship with the ball valve, particularly when it is shifted to its closed position wherein the fluid passage through the valve is disposed transversely to the bore of the annular seal, hence, closing the fluid conduit in which the valve is mounted. Ball valves are customarily operated by a camming sleeve or by a pair of diametrically opposed camming sleeve segments, which incorporate cam slots which respectively receive radially projecting, diameterically opposed pins projecting from the periphery of the ball valve and offset from the center thereof. Axial movement of the camming sleeve or sleeve segments thus effects a 90.degree. rotation of the ball valve required to move it from a fully opened to a fully closed position.
With a ball valve of the type described and illustrated in the aforementioned co-pending application, it has been observed that when the valve is shifted to its fully opened position, the valve is subject to displacement from the fully opened position through impacts received from wire lines and tools suspended from such wire lines, which are inserted through the central fluid passage of the ball valve. Any such movement of the ball valve from a fully opened position can interfere with the subsequent removal of the wire line tool, and hence it is desirable that the ball valve, once it is moved to an opened position, be locked in such opened position, at least to the extent that it is not subject to displacement by impacts received from wire line tools passing therethrough.